The present invention relates to apparatus and methods for inserting an intraocular lens into an eye. More particularly, the invention relates to such apparatus and methods wherein the desired insertion of the lens is easily, controllably and effectively achieved.
An intraocular lens (IOL) is implanted in the eye, for example, as a replacement for the natural crystalline lens after cataract surgery or to alter the optical properties of (provide vision correction to) an eye in which the natural lens remains. IOLs often include an optic, and preferably at least one flexible fixation member or haptic, which extends from the optic and becomes affixed in the eye to secure the lens in position. The optic of the IOL normally includes an optically clear lens. Implantation of such IOLs into the eye involves making an incision in the eye. Making the incision as small as possible reduces trauma and speeds healing.
IOLs are known which are foldable (deformable) so that the IOL can be inserted into the eye through an incision smaller than the diameter of the lens and subsequently permitted to unfold after it has passed through the incision. A substantial number of instruments have been devised to aid in inserting such a foldable lens into the eye. The advantages of the foldable lens in cataract removal and lens replacement are so significant that many of the lens replacement procedures are performed with folded lenses inserted into the eye, and released therein to assume their initial unfolded state.
Some of the most generally accepted insertion apparatus employ a hollow insertion tube having a diameter which permits the folded IOL to pass through the hollow space defined by the tube without permanent deformation, and a plunger assembly including a rod, often made of metal, which is moved longitudinally in the hollow space in contact with the optic of the IOL to push the IOL through the hollow space.
Several disadvantages are apparent in such insertion devices. For example, pushing, without trapping or holding, the IOL through and out of the hollow space defined by the tube can cause the IOL to be released from the insertion device without precise control, so that the released IOL may damage the eye and/or may be mispositioned in the eye. In addition, the metal rod can result in marking the surface of the optic and/or even tearing the optic, particularly when the optic is made of soft materials, such as soft elastomeric silicone polymeric materials. Also, the metal rod has a tendency to by-pass the IOL in the hollow space. That is, the rod as it is being moved distally through the hollow space may actually pass through a fold in the folded optic. If this occurs, the rod becomes ineffective to push the IOL through the hollow space. This problem has been avoided in the past by increasing the cross-sectional area of the rod. However, a rod with a large cross-sectional area presents its own problems. For example, pushing such a large rod through the hollow space can damage the IOL and/or the inserter or result in an uncontrolled release of the IOL into the eye, possibly with inserter debris being disadvantageously introduced into the eye.
Stoy et al U.S. Pat. No. 4,919,130 discloses a rod-type IOL insertion device including two separate rods. This patent discloses a cup-shaped head of soft material, such as a silicone elastomer, detachably connected at the distal end of the second rod which pushes a compressed IOL through the cannula or tube. Although this cup-shaped head may avoid scratching or tearing the lens during the pushing operation, its cup-shaped distal face does nothing to increase the control the surgeon has in releasing the IOL in the eye. In addition, this cup-shaped head is relatively short, in the axial direction, which can result in the head becoming separated from the rod in the eye. This can result in an additional procedure to remove the head from the eye, which is traumatic for the patient.
One further disadvantage of using a soft head or tip is the need to place the head or tip on the rod and then to remove it, for example, after use for disposal. Because such heads tend to be relatively small, it is often difficult and time and labor consuming to apply the head to the rod manually and to remove the head from the rod manually.
The disclosure of commonly assigned U.S. patent application Ser. No. (Attorney's Docket No. D-2710) filed on even date herewith is incorporated by reference in its entirety herein.
It would be advantageous to provide IOL insertion apparatus and methods which facilitate the use of soft heads or tips to enhance the advantages of using such soft heads or tips on the rods of IOL insertion apparatus.